The invention relates to block copolymers with siloxane blocks which are linked via rigid spacers and to their use as surface-active agents.
According to the prior art there are a large number of surface-active siloxane block copolymers which are used in a broad range of industrial applications. They may be either methylpolysiloxanes (see DE-C-25 33 074) or (pseudo)haloalkyl-substituted siloxanes (see DE-C-36 26 297, U.S. Pat. No. 3 952 038 or DE-A-24 02 690), which are used, for example, as cell regulators in highly elastic, cold-curing polyurethane foams. Moreover, a broad range of silicone polyether copolymers, and their use as surface-active substances, is known, as is described, for example, by way of example in the following patents:
DE-C-15 70 647: chloropolysiloxanyl sulfates are reacted with mixtures of alkylene oxide adducts which consist of from 50 to 96 OH equivalent percent of polyalkylene glycol monoethers, which consist of ethylene oxide units and propylene oxide units and have a content of from 40 to 70% by weight of oxypropylene units and a molar weight of from 1000 to 3000, whose hydroxyl groups are preferably secondary, and
from 5 to 50 OH equivalent percent of alkylene oxide adducts of poly-functional hydroxyl compounds with a molar weight of from 130 to 3500, whose polyalkylene glycol component consists of ethylene oxide units and/or propylene oxide units and which have an OH equivalent weight of up to 1750 and whose hydroxyl groups are preferably secondary, and
the proportions being chosen such that there are not more than 1.4, preferably from 1.05 to 1.2, OH equivalents per acid equivalent of the chloropolysiloxanyl sulfate.
DE-C-16 94 366: Use is made as foam stabilizers of polysiloxane-polyoxyalkylene block copolymers whose polysiloxane block has a conventional composition but whose polyoxyalkylene block consists of
from 25 to 70% by weight of a polyoxyalkylene having an average molecular weight of from 1600 to 4000 and an ethylene oxide content of from 20 to 100% by weight, the remainder being propylene oxide and, if desired, higher alkylene oxides, and
from 30 to 75% by weight of a polyoxyalkylene having an average molecular weight of from 400 to 1200 and an ethylene oxide content of from 65 to 100% by weight, the remainder being propylene oxide and, if desired, higher alkylene oxides.
DE-A-25 41 865: The polysiloxane-polyoxyalkylene block copolymers are defined with respect to their polyoxyalkylene blocks such that one polyoxyalkylene block has a mean molar weight of from 900 to 1300 and consists to the extent of from 30 to 55% by weight of ethylene oxide, the remainder being propylene oxide, and the other polyoxyalkylene block has a mean molar weight of from 3800 to 5000 and consists to the extent of from 30 to 50% by weight of ethylene oxide, the remainder being propylene oxide.
EP-A-0 275 563: The block copolymer described in this patent application comprises three different polyoxyalkylene blocks, namely a block containing from 20 to 60% by weight of oxyethylene units, at a molar weight of from 3000 to 5000, a further block with from 20 to 60% by weight of oxyethylene units and a molar weight of from 800 to 2900, and a third block comprising only polyoxypropylene units and having a molar weight of from 130 to 1200.
In addition, the patent literature describes siloxane block copolymers which are employed as emulsifiers and in which both polyoxyalkylene groups and long-chain alkyl groups are attached to linear polysiloxanes (see for example U.S. Pat. No. 3,234,252, U.S. Pat. No. 4,047,958 or DE-C-34 36 177).
Further patent documents (e.g. U.S. Pat. No. 5,136,068, EP-A-0 381 318 and EP-A-0 529 847) describe surface-active siloxane block copolymers, for use as emulsifiers, in which polyoxyalkylene radicals and long-chain alkyl radicals are attached to the polysiloxane and there is additional linking of the siloxane block copolymer via a divalent organic radical. The feature of the siloxane block copolymers described is that linking is in every case obtained by reaction of SiH groups with, for example, diolefins, divinylbenzene or 1,3-divinyltetramethyldi-siloxane. In the course of such a reaction, moveable bridging links (spacers) are formed.
Despite the large number of different active substances obtainable in this way, the complexity of the applications (nonhomogeneous, in some cases multiphase combinations of raw materials in multivariant compositions for applications which have not been fully rationalized, such as cosmetics, emulsion technology, multiphase polymerization, etc.) dictates the necessity of searching for further improved structures. An example of such an optimization requirement for additives having surface-active properties is the production of polyurethane foams. This optimization requirement results, on one hand, from the large number of possible polyurethane foam types, for example flexible foam, rigid foam, ester foam, cold-cure foam, packaging foam, flame-laminable foam, molded foam, integral foam, etc., and on the other hand also from recent foaming techniques, such as variable pressure foaming, foaming techniques using pressurized inert gases, or forced cooling processes (e.g. ENVIRO-CURE, CRAIN INDUSTRIES).
Surprisingly it has now been found that the introduction of rigid spacers between spatially separate siloxane blocks in a molecule produces astonishing effects in a variety of performance tests.
The present invention provides innovative structures whose feature is that within one molecule siloxane blocks are attached via a rigid spacer. The distance thus established between the siloxane units is therefore not, as in the case of simple linear or nonpolycyclic structures, variable as a result of the free mobility (xe2x80x9cflexibilityxe2x80x9d) of the bond. For synthesizing the novel structures, the use of 2,5-norbornadiene (bicyclo[2.2.1]hepta-2,5-diene) has proven particularly suitable. Accordingly, the claimed structures feature linking of siloxane blocks via 
which is expressed below by the device 
The invention therefore provides block copolymers of the general average formula: 
where the radicals and indices have the following meaning:
A=radical R1, radical E or a radical of the formula IIa 
or a radical of the formula IIb 
B=radical of the formula IIa or IIb
D=radical of formula 
R1=an alkyl radical having 1 to 30 carbon atoms, a substituted alkyl radical, an optionally substituted aryl radical or an optionally substituted alkaryl radical, with at least 80% of the radicals R1 being methyl groups,
a is from 3 to 200,
b is from 0 to 50,
c is from 0 to 10 and
d is from 0 to 5, it being possible for the values of a, b, c and d in the individual segments Z of the radicals A, B and D to be different,
E=radical which is
a) a radical of the general formula
xe2x80x94R2fxe2x80x94Oxe2x80x94(CmH2mOxe2x80x94)nR3
where
R2 is a divalent alkyl radical, which can also be branched, and
f is 0 or 1,
m is on average 2 to 4,
n is from 0 to 100 and
R3 is a hydrogen radical, an optionally substituted alkyl radical having 1 to 6 carbon atoms, an acyl radical or a radical xe2x80x94Oxe2x80x94COxe2x80x94NHxe2x80x94R4 in which R4 is an optionally substituted alkyl or aryl radical, and/or
b) has the meaning of an epoxy-functionalized alkyl substituent which optionally contains heteroatoms, and/or
c) has the meaning of a mono-, di- and trihydroxyalkyl substituent which can also be aromatic or branched and partially or completely etherified or esterified, and/or
d) has the meaning of a halo- or pseudohalo-substituted alkyl, aryl or aralkyl radical which optionally can also be branched,
with the proviso that at least one radical of the formula IIa or IIb is present in the molecule.
In this context it is also possible to employ various substituents in combination, as described, for example, in DE-C-42 29 402 for polyether substituents. The substituents may optionally be different, for example in their molar mass, in the case of polyethers possibly in their end group R3, or in the proportions of the monomers used, in the nature of the monomers, etc.
The bridging link (spacer) 
between the siloxane segments is formed by the reaction of 2,5-norbornadiene with SiH groups. Per molecule of the novel substances there must be at least one radical 
The molecule obtained by linking ought to contain xe2x89xa6600 Si atoms.
Those knowledgeable in the art are aware that the molecules obtained represent a mixture with a distribution given mainly by statistical rules. The values for a, b, c, d, n and the number of the radicals 
per molecule therefore correspond to mean values.
A small proportion of the radicals R1 can be a hydrogen radical, specifically when the hydridosiloxanes employed do not react completely with the olefinically unsaturated compounds employed (e.g. allyl polyethers, olefins, allyl glycidyl ether, etc.) and with the 2,5-norbornadiene.
Depending on the desired application, various ranges are preferred from the group of the claimed compounds:
For applications in connection with the preparation of flexible polyurethane slabstock foams, for example, preference is given to compounds where b greater than 3 and 5 less than (a+c+d)/b less than 20, but particular preference is given to products having an average m in the molecule of 2.3 less than m less than 3.1, and very particular preference to products having an average m in the molecule of 2.5 less than m less than 2.8.
For application in connection with the preparation of rigid polyurethane foam or polyurethane ester foam, preferred compounds are those having an average n in the molecule of n less than 28, and particularly preferred compounds are those having an average m in the molecule of m less than 2.5, and very particularly preferred compounds are those having an average quotient (a+c+d)/b in the molecule of (a+c+d)/b less than 8.
For applications in connection with the preparation of cold-cured molded foams, preferred compounds are those having an average b in the molecule of b less than 5 and particularly preferred compounds are those having an overall number of radicals E less than 7.
For applications in cosmetics or as emulsifier, compounds are preferred in which at least 60% of the radicals R3 are hydrogen radicals; particular preference is given to compounds in which at least 80% of the radicals R3 are hydrogen radicals and very particular preference is given to compounds in which all radicals R3 are hydrogen radicals and the average value of m in the molecule is less than 2.3.
For applications as an additive in the paints and coatings field, preference is given to those compounds in which at least 80% of the radicals R3 are hydrogen radicals. Particular preference is given to those compounds in which the radical E has the meaning of an epoxy-functionalized alkyl substituent.